In the following, the structure of a mobile communication network will be described with a prior art GSM mobile communication network of FIG. 1 as an example. Communication between a Mobile Station (MS) within a cell and the network takes place on the radio path via a Base Transceiver Station (BTS). The base transceiver stations are coupled to a Base Station Controller (BSC), which usually controls several base stations. The location of the MS is known with an accuracy of a so-called Location Area (LA), constituted by a few cells. The mobile station may roam within the location area without updating its location data. Several base station controllers are coupled to a Mobile Services Switching Center (MSC), which carries out the principal switching functions of the mobile communication network. The entirety of cells under control of the MSC is referred to as an MSC area; all calls originating from this area and terminating therein are forwarded via this MSC. In addition, it connects the mobile communication network to external networks and via a so-called gateway MSC to mobile communication networks of other operators.
A mobile communication network also comprises different kinds of databases. A Home Location Register (HLR) permanently stores a subscriber's data regardless of his current location. Subscriber data obtained from the HLR are stored in a Visitor Location Register (VLR) during the subscriber's visit to the VLR area.
In order for the operator to be able to charge the subscriber for calls and services, the traffic management part of the network has a mechanism by means of which a sufficient amount of data will be stored for every service to be charged. The most significant traffic-related charging basis is constituted by calls. In the MSC, a so-called Toll Ticket record is produced for each call as soon as it has ended, containing all the necessary information to calculate the charges for the call. The contents of the record depend on the switching center technique being employed and the operator requirements. The gateway MSC exchanges messages with the HLR in accordance with a MAP/C protocol, and the prior art message exchanging enables including at least the following data in the TT record fields:
(a) at first, identifiers, i.e. the subscriber's IMS number and the identifier of the MSC that generated the record, PA1 (b) secondly, the type of the call, i.e. whether the call is a mobile originating call or a mobile terminating call forwarded by the MSC (this means that the TT record also contains routing information from the switching center to the mobile station), PA1 (c) if the switching center is a gateway MSC, the record contains routing information GMSC-MS, PA1 (d) mobile terminating call re-routing information GMSC-MSC, if the MSC is in another network, PA1 (e) call status, i.e. information on whether the call succeeded or failed. The data of failed calls are only utilized for statistical purposes, and therefore the manufacturer of the switching center does not always include it in the TT information, PA1 (f) date, call begin moment, duration and nature. The last one indicates whether speech, data, a short message etc is in question, PA1 (g) the number of the calling party (in mobile terminating calls) or the number of the called party (in mobile originating calls), PA1 (h) charging, collected by the target operator from the subscriber's operator in cases of roaming, PA1 (i) cell information (Cell ID), indicating the cell of the incoming/outgoing call.
The fields listed above are exemplary only, and the supplier of the switching center may add other fields according to the operator's requirements. The TT records are stored in an I/O apparatus of the MSC as a file which is at predetermined intervals transferred to a charging system for further processing. Typically, the transfer is carried out at intervals of 5 to 15 minutes, which therefore represents the real time delay for the data.
The chart of FIG. 2 illustrates the use of the aforementioned parameters in a TT record. The fields of the record include the numbers of subscribers a and b, date, time of call begin and end, route, cell ID, call charging pulses and an EOS field. The EOS (End of Selection) is a clear code defining the reason why the call did not go through. There may be in use as many as 1000 different codes. Code 0 means that a call succeeded, and a code other than 0 indicates not only a failed call but a reason for it as well.
As the mobile communication network expands and call intensity varies, the network must continuously be modified. Increase in capacity can be provided by adding new TRX units in the cell, and by adding new nodes (MSCs and BSCs) and new cells whereby the transmission routes also change. To carry out the changes, and for operation, maintenance and managing functions the network produces, from several locations, different kind of information; the BSC, for example, collects information from the cells it controls, whereby information on traffic intensity is obtained as a function of time. Information obtained from various sources has to be gathered and processed in a centralized manner. In this respect, a mobile communication network does not differ from other telecommunication networks.
In present-day mobile communication networks, a drawback of traffic management concerns poor real time representativeness. Information on peaks is only available a long time afterwards. Although the information on changes in traffic intensity is available, this is only after a long delay and in an unillustrative numerical form. As a result, traffic capacity in some cells may run out, because dynamic allocation of traffic capacity in real time, or practically in real time, is not possible.
An object of the present invention is a system which makes traffic management easier by providing a visually illustrative representation of traffic intensity and changes therein in practically real time. The system should be possible to couple to an MSC of any manufacturer, without need to change its internal functions.
This object is achieved with a system set forth in claim 1.
The management system is realized so that the TT file which is obtained from the MSCs of the mobile communication network and which contains TT records is read and transferred to be incorporated into a database of the traffic management system. Traffic management software processes information obtained from the records, counts the number of calls carried out in the cells, and produces a hierarchical graphic representation of the information on a map display. The term "hierarchical" here means that the highest level is the entire geographical area, with possibly several MSCs, under control of one operator. The subsequent level may be an area of one MSC, and the subsequent level may be a location area. The lowest level is represented by one cell. Each level shows traffic intensity with grades of color, i.e. the more traffic is present the stronger the color. The display is automatically updated as the MSC provides the TT data.
The management system also contains logic for traffic load monitoring. This logic monitors the traffic load on the network on different levels and in different cells. If the traffic load in an area, within a cell or cells, exceeds a predetermined level, the software automatically transmits a command to the base station controller in question to distribute traffic between the overloaded cell and the neighbouring cells. This can be done by changing the handover criteria by advancing handovers at cell borders from an overloaded cell to a cell with less traffic load, and correspondingly delaying handover to an overloaded cell. The above can be referred to as logically reducing the size of an overloaded cell. If at the base station there is an additional so-called floating TRX unit available, it can be coupled for use in the overloaded cell and accordingly increase the cell capacity.
The calculation results can be stored for statistical purposes. The statistical data may constitute for example congestion statistics, average duration of calls per channel, degree of channel utilization, etc.